The reactor chamber of the fluidized bed reactor typically comprises an interior that is rectangular of a horizontal cross section, defined by four side walls, a bottom and a roof, in which interior, bed material containing solid material and, for example, fuel is fluidized by means of fluidizing gas, generally, oxygenous, primary gas required for the exothermic chemical reactions taking place in the reaction chamber. The interior, in other words, the reaction chamber, is called a combustion chamber and the reactor a fluidized bed boiler, when a combustion process is performed in the fluidized bed reactor. The side walls of the reaction chamber are typically also provided at least with conduits for fuel feed and feed of secondary air.
The side walls of the reaction chamber are generally fabricated to comprise panels formed of tubes and fins therebetween, whereby the energy released in the chemical reactions of the fuel is used to evaporate the water flowing in the tubes. Superheater surfaces are also often provided in a fluidized bed reactor to further increase the energy content of the steam.
A fluidized bed reactor may be, for example, a circulating fluidized bed reactor or a bubbling bed reactor. Fluidized bed reactors are used in various combustion processes, heat exchange processes, chemical processes, and metallurgical processes. In the combustion processes, components of the fluidized bed may include granular fuels, like coal, coke, lignite, wood, waste or peat, and also, other granular substances, like sand, ash, desulfurizing agents or catalysts.
A characteristic feature of the fluidized bed reactor is the use of solid bed material as process material. The bed material acts as, for example, a temperature stabilizing component in the reaction chamber and binds a considerable amount of heat therein. Bed material can thus also be used for transferring heat from the reaction to the medium. In fluidized bed combustion plants, heat recovery typically takes place in a combustion chamber and in a convection portion by means of heat exchange surfaces, which is arranged downstream of a particle separator in the gas flow. Heat exchange surfaces, such as superheaters, are typically arranged, for example, in a free space in the upper portion of the reaction chamber and in the convection portion subsequent thereto, in order to superheat steam.
In the fluidized bed reactors, it is known per se to use heat exchanger chambers for solids separated from the reaction chamber, i.e., fluidized bed heat exchangers, to which bed material can be supplied from the reaction chamber and cooled in the fluidized bed heat exchanger, for example, prior to recirculating the solids back to bed material of the reaction chamber.
Such fluidized bed heat exchangers typically operate as a so-called bubbling bed. The heat exchange chamber can be arranged either inside the reactor itself or outside thereof. Finnish patent publication No. F1-119916 discloses such a heat exchange chamber arranged inside of the reactor. When the heat exchange chamber is inside the reactor, it is preferably supported by means of the walls and/or the bottom portion of the reactor.
International Publication WO 94/22571 discloses a heat exchange chamber, which is arranged outside of the actual reaction chamber. The heat exchange chamber is arranged in connection with the circulating fluidized bed reactor in such a manner that it participates in a so-called internal circulation for the solids. There, part of the bed material flow inside the reaction chamber is guided directly from the reaction chamber to the heat exchange chamber and, from there, back to the reaction chamber.
U.S. Pat. No. 4,896,717 discloses a heat exchange chamber, which is outside of the actual reactor. Here, the heat exchange chamber is connected to the external circulation for the solids in the circulating fluidized bed reactor, in other words, the solids led to the heat exchange chamber are separated from the gas exiting the reaction chamber.
The support and connection of the heat exchange chamber for solids separated from the reaction chamber to the actual reaction chamber is problematic, especially, in that the heat exchange chamber, horizontally extending far from the reaction chamber, i.e., at least partially outside of the plane of the side wall of the reaction chamber, requires a separate support, which takes up space around the reaction chamber and, thus, diminishes the possibilities to position auxiliary equipment. For example, the heat exchange chamber disclosed in U.S. Pat. No. 4,896,717 extends far under the solids separator, so, in practice, it must be supported very strongly, for example, by supporting it from the cyclone above, whereby only a portion of the mass thereof transfers to the wall of the reaction chamber.
Although the fluidized bed reactors known from the prior art are advantageous as such, a need has arisen recently to provide an improved fluidized bed reactor, in which a heat exchange chamber is connected to the fluidized bed reactor in an improved manner.
Objects of the invention are achieved by means of a fluidized bed reactor arrangement, in which the fluidized bed reactor comprises at least a bottom portion, a roof portion and at least one side wall vertically extending between the bottom portion and the roof portion, which side wall is arranged at the lower portion thereof, inclined in such a manner that the cross section of the reaction chamber of the reactor decreases towards the bottom portion, and which fluidized bed reactor arrangement comprises a heat exchange chamber outside of the reaction chamber at an area of the side wall that is arranged to be inclined, and which side wall, that is inclined at the lower portion thereof extending between the bottom portion and roof portion, forms a partition wall between the heat exchange chamber and the reaction chamber, and in which fluidized bed reactor arrangement, the heat exchange chamber extends from the partition wall to the other side of the plane extending via the side wall. It is characteristic of the invention that the rear wall of the heat exchange chamber is connected to the side wall of the reaction chamber from the upper portion of the rear wall at a connection area in such a manner that the direction thereof aligns with the direction of the side wall at least in the connection area.
Thus, the transfer of the mass forces of the heat exchange chamber to the reaction chamber can be arranged in an advantageous manner by supporting the heat exchange chamber substantially completely to the reaction chamber. Thus, substantially the major portion of the mass forces thereof, preferably, substantially all of the mass forces, are directed to the reaction chamber. Thereby, no such separate support structures are required for the heat exchange chamber, which support the heat exchange chanber to the foundation or to the supporting framework of the fluidized bed arrangement.